Sugar and Dental Caries

Transcription

1 WSRO POSITION STATEMENT Sugar and Dental Caries 1 Written November 2011 Background The World Oral Health Report (2003) reported a vast reduction in worldwide dental caries experience between 1980 and However, dental caries continues to be a major health problem, particularly in the developing world. Dental caries occur when acid-producing bacteria, especially Mutans streptococci, Lactobacilli and Actinomyces species, populate the sticky coating (plaque) on the surface of the tooth. These bacteria convert fermentable carbohydrates such as glucose, fructose, sucrose and maltose (which may be derived from hydrolysis of cooked starches by salivary amylase) into lactic acid, thus making plaque acidic. The acidic plaque causes demineralisation of the tooth enamel and, if unchecked, the underlying dentine. The presence of bacteria and fermentable carbohydrates are not the sole factors which can affect dental caries. Other factors include the innate susceptibility of tooth surfaces, frequency of eating, intrinsic properties of the foodstuff affecting food clearance, oral hygiene practices, fluoride availability, genetic factors, and salivary flow and composition. Saliva contains protective minerals (calcium) and buffers which aid in re-mineralisation of the tooth enamel and neutralisation of the acid environment. Saliva is also a reservoir for fluoride which exerts its protective effects by reducing the effectiveness of acidogenic bacteria or the susceptibility of enamel to acid dissolution. Under normal circumstances, the demineralisation that occurs following any eating occasion involving fermentable carbohydrates is repaired by the replacement of lost material with minerals from saliva. However, if the balance between demineralisation and repair favors demineralisation, as a result of frequent consumption of carbohydrate substrates for these acidogenic bacteria, a focal area where the enamel structure becomes porous may result. This is called a white spot lesion and may repair spontaneously. If acid attack endures, without the natural repair process being able to correct demineralisation, then further loss of the tooth surface architecture may occur and result in bacterial invasion into the resulting cavity. At this stage spontaneous repair is unlikely and the cavity will require treatment to prevent further damage. The significance of sugar in influencing the dental caries process has been the subject of research and debate for more than 100 years. A role for amount of sugar? Researchers have employed ecological studies in order to determine whether a relationship exists between sugar intake and prevalence of dental caries. Sreebny (1982) reported a significant linear relationship between sugar supply and dental caries prevalence in a cross-sectional study of 12-y old children across 47 countries. Sugar supply was estimated to explain approximately 50% of the variance in caries experience. However, there was no apparent relationship in 5-y old children. A later re-examination of the relationship, with a much larger data set, reduced the estimated proportion of the variance attributable to the amount of sugar in the food

2 supply by more than half (Woodward and Walker, 1994). Furthermore, examination of the data from only developed countries showed no relationship between sugar supply and caries. These findings suggest that, in both the developed and developing world, other factors are more important than sugar supply in determining caries experience. Sreebny (1982) proposed a cut-off of 50 g sugar per person per day to minimise risk of caries. This suggestion was taken into account by the WHO/FAO (2003) who proposed a similar cut-off of 6 10% energy as free sugars (defined as all mono- and disaccharides added to foods, plus sugars naturally present in honey, syrups and fruit juices). This recommendation was made despite evidence to the contrary (Gustaffson et al., 1954, Ruxton et al., 1999, Woodward and Walker, 1994). Although the relatively small reduction in caries experience during war-time rationing of sugar is consistent with a role for sugar supply in the caries process, the most substantial reduction in dental caries during the past 40 years has occurred following the introduction of fluoridated water or toothpaste and improved oral hygiene (Kandelman, 1997, Konig, 1990). Trends in caries reduction in industrialised countries have occurred not only independent of sugar intake, but also whilst sugar consumption has stayed relatively constant (Downer, 1994, Konig, 1990). Indeed, population data show no relationship between changes in sugar supply and changes in caries prevalence (Ruxton et al., 1999). Furthermore, the evidence does not support the proposition that even total removal of sugar (added, free or NMES) from the diet would eliminate caries (Konig, 1990, Woodward and Walker, 1994). This is explicable in the light of the evidence that all fermentable carbohydrate, including the staple food cooked starch, is acidogenic in the presence saliva and certain oral bacterial populations. The results of smaller longitudinal population and intervention studies have not indicated a strong relationship between sugar intake and caries incidence. A two year study on English school children reported a significant relationship between consumption of sugars and caries, although sugars consumption could only explain 2% of the variance in caries incidence (Rugg-Gunn et al., 1984). A 100% increase in sugar consumption in children, prior to modern oral health practices and ethical considerations, did not result in a significant effect on caries development (King, 1955). Furthermore, a 5-year study in Sweden (Gustaffson et al., 1954) showed no influence of amount of sugar consumed when 340 g per day was given only at meal times to subjects with no access to fluoride and no oral hygiene. Free living individuals today are unlikely to consume such huge amounts of sugar and many will have the protection of both oral hygiene and access to fluoride. A role for frequency of sugar intake? Frequent snacking of fermentable carbohydrates, particularly in the absence of adequate oral hygiene, may not allow time for sufficient buffering of the tooth environment or remineralisation via salivary action. In the absence of oral hygiene, the classic experiment of Gustafsson et al., (1954) showed that frequency of sugar consumption was far more important in influencing dental caries than amount. Duggal et al., (2001) showed that twice daily use of fluoride toothpaste increased the frequency with which a 12% sugar solution could be imbibed from 4 up to 7 times a day without significant enamel demineralisation. The authors speculated that tooth 2

3 brushing twice daily with fluoride toothpaste might allow fermentable carbohydrates to be consumed up to 5 times a day without increasing the risk of caries. In contrast, Gibson and Williams (1999) reported frequency of consumption of all sugary foods (including soft drinks) was not associated with caries experience in preschool children regardless of reported tooth brushing frequency. However, in this study, an association of caries with consumption of sugar confectionery (both amount as %energy and frequency) was seen in children who brushed their teeth once a day or less. In addition to the confounding effects of oral hygiene, food clearance, bacterial and salivary levels, it is difficult to isolate the effect of frequency from amount in observational studies of populations as the two may be strongly correlated (Rugg-Gunn, 1993). However, a recent review of observational epidemiological studies reported a more significant relationship of frequency than quantity of sugar with dental caries (Anderson et al., 2009). Some agencies recommend frequency of sugars consumption should be limited to no more than 4 times a day (DoH, 2009, WHO/FAO, 2003) but fail to mention other fermentable carbohydrates. Intrinsic, extrinsic, added, free sugars and NMES? Organisations frequently provide recommendations depending on whether the sugar is naturally found within a foodstuff or has been added in processing. Sugars may be defined as: intrinsic found naturally within the cell in unprocessed food, or extrinsic or free found outside of the cell. Extrinsic sugars comprise sugars naturally present in honey, syrups and fruit juices, as well as sugars added to foods at the table or in processing. Milk sugar (lactose), being natural, although an extrinsic sugar, is often considered a special case. Therefore, extrinsic sugars may be referred to as non-milk extrinsic sugars (NMES). The recommendations from certain agencies with regard to sugar intake and risk of dental caries are only for added, free or NMES sugars (DoH, 1989, WHO/FAO, 2003). However, the evidence does not support a differential effect of intrinsic versus extrinsic sugars (added, or free or NMES) with regard to acid production (Beighton et al., 2004) or enamel demineralisation (Issa et al., 2011). Indeed, an expert group convened by WHO and FAO specifically recommended that these terms should not be used as they are unhelpful and confusing (Cummings and Stephen, 2007). Recommendations for sugar and dental caries risk The advice regarding sugar and oral health is inconsistent. Sugar intake is still viewed by many agencies, including Australia (NHMRC, 2003) and the UK (DoH, 1989, 2005, 2009) as a prime, if not the main cause of dental caries. The latter organisation recommends for NMES not to exceed 11% of food energy, and for sugars to not be consumed more than 4 times a day. These recommendations approximate those of the WHO/FAO (2003), and are inconsistent with an earlier FAO/WHO report (1997) which recognised the multi-factorial cause of dental caries and suggested that programmes should focus on fluoridation and oral hygiene and not on sucrose intake alone. Conversely, the IOM (2002) was not able to determine, from the available evidence, an intake of sugars at which increased risk of dental caries could occur. Similarly, EFSA (2010) were not able to set an upper limit for intake of added sugars to reduce risk of dental caries. The US Dietary Guidelines (USDA/HHS, 2005) suggest that frequency and duration of exposure of all fermentable carbohydrates should be reduced and oral hygiene practices optimised. Similarly, EFSA (2010) state that frequent consumption of sugar-containing foods 3

4 can increase risk of dental caries, particularly when oral hygiene and fluoride prophylaxis are insufficient. Fluoride The use of fluoride toothpaste has proved to be the most successful approach to the prevention of dental caries. Fluoridation of water supplies is also beneficial but appears to be less effective than regular use of fluoride toothpaste. A review of the evidence for the effectiveness of dental health education was prepared for the UK DoH (Kay and Locker, 1996) and reported persuasive evidence supporting education regarding fluoride use, whereas dietary approaches did not appear to be worthwhile. The introduction of fluoride toothpaste has been remarkably successful in reducing caries prevalence among children and adults (Cottrell, 2011). Statement Frequent consumption of fermentable carbohydrates, including sucrose, has a role in the aetiology of dental caries. However, this role is substantially reduced when oral hygiene with use of fluoride toothpaste is adequate. Efforts to prevent dental caries should focus on achieving adequate oral hygiene practices with fluoride toothpaste as this has proven to provide a much greater reduction in caries experience than dietary modification. Dietary advice for the reduction of dental caries risk should focus on limiting the frequency of exposure to all fermentable carbohydrates. References Anderson, C. A., Curzon, M. E., Van Loveren, C., et al. (2009) Sucrose and dental caries: a review of the evidence. Obes Rev, 10 Suppl 1, Beighton, D., Brailsford, S. R., Gilbert, S. C., et al. (2004) Intra-oral acid production associated with eating whole or pulped raw fruits. Caries Res, 38, Cottrell, R. C. (2011) Dental disease: Etiology and epidemiology. IN CABALLERO, B., ALLEN, N. & PRENTICE, A. M. (Eds.) Encyclopaedia of Human Nutrition. 2nd Edition ed. Kidlington, UK, Elsevier Academic Press. Cummings, J. H. & Stephen, A. M. (2007) Carbohydrate terminology and classification. Eur J Clin Nutr, 61 Suppl 1, S5-18. DoH (1989) Dietary Sugars and Human Disease. Committee on Medical Aspects of Food Policy. Report on Health & Social Subjects No 37. London, HMSO. DoH (2005) Choosing better oral health: an oral health plan for England DoH (2009) Delivering Better Oral Health. An evidence-based toolkit for prevention - second edition. Downer, M. C. (1994) Caries prevalence in the United Kingdom. Int Dent J, 44, Duggal, M. S., Toumba, K. J., Amaechi, B. T., et al. (2001) Enamel demineralization in situ with various frequencies of carbohydrate consumption with and without fluoride toothpaste. J Dent Res, 80, EFSA (2010) Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre. EFSA Journal, 8, FAO/WHO (1997) Carbohydrates in human nutrition (FAO Food and Nutrition Paper - 66) Gibson, S. & Williams, S. (1999) Dental caries in pre-school children: associations with social class, toothbrushing habit and consumption of sugars and sugar- 4

5 containing foods. Further analysis of data from the National Diet and Nutrition Survey of children aged years. Caries Res, 33, Gustaffson, B. E., Quensel, C.-E., Swenander, L. L., et al. (1954) The Vipeholm Dental Caries Study. The effects of different levels of carbohydrate intake in 436 individuals observed for five years. Acta Odontol Scand, 11, IOM (2002) Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, proteins, and amino acids Issa, A. I., Toumba, K. J., Preston, A. J., et al. (2011) Comparison of the Effects of Whole and Juiced Fruits and Vegetables on Enamel Demineralisation in situ. Caries Res, 45, Kandelman, D. (1997) Sugar, alternative sweeteners and meal frequency in relation to caries prevention: new perspectives. Br J Nutr, 77 Suppl 1, S Kay, E. J. & Locker, D. (1996) Is dental health education effective? A systematic review of current evidence. Community Dent Oral Epidemiol, 24, King, J. D. e. a. (1955) The effect of sugar supplements on dental caries in children OFFICE, H. M. S., London Konig, K. G. (1990) Changes in the prevalence of dental caries: how much can be attributed to diet? Caries Res, 24, NHMRC (2003) Dietary Guidelines for Australian Adults. IN AUSTRALIA, T. C. O. (Ed.). Canberra. Rugg-Gunn, A. J. (1993) Nutrition and Dental Health, Oxford, Oxford Medical Publications. Rugg-Gunn, A. J., Hackett, A. F., Appleton, D. R., et al. (1984) Relationship between dietary habits and caries increment assessed over two years in 405 English adolescent school children. Arch Oral Biol, 29, Ruxton, C. H., Garceau, F. J. & Cottrell, R. C. (1999) Guidelines for sugar consumption in Europe: is a quantitative approach justified? Eur J Clin Nutr, 53, Sreebny, L. M. (1982) Sugar availability, sugar consumption and dental caries. Community Dent Oral Epidemiol, 10, 1-7. USDA/HHS (2005) Dietary Guidelines for Americans, WHO (2003) The World Oral Health Report WHO/FAO (2003) Diet, nutrition and the prevention of chronic diseases. Woodward, M. & Walker, A. R. (1994) Sugar consumption and dental caries: evidence from 90 countries. Br Dent J, 176,